With rapid development of the microelectronics industry, the research and development of high-end scanning lithography tool for manufacturing large scale integrated circuit has become an urgent demand. The illumination system may provide high illumination uniformity, control exposure dose, and implement off-axis illumination for the lithography tool to improve the resolution and increase the depth of the focus, and it is an important part of the lithography tool. So the performance of the illumination system may directly affect the performance of the lithography tool.
U.S. Pat. No. 7,187,430B and an article entitled “Generation of arbitrary freeform source shapes using advanced illumination systems in high-NA immersion scanners” by Jorg Zimmermann et al., Proc. of SPIE, Vol.7640, 764005(2010), both disclose a general lithography illumination system as shown in FIG. 1. The system includes a laser light source 1, a collimating and expanding unit 2, a pupil shaping unit 3, a first micro-lens array 4, a second micro-lens array 5, a condenser lens group 6, a scanning slit 7, an illumination lens group 8, and a mask 9, where the first micro-lens array 4 and the second micro-lens array 5 form a homogenizer unit of the lithography illumination system. A laser beam goes through the collimating and expanding unit 2 and pupil shaping unit 3 to form a required illumination mode. The laser beam is homogenized by the homogenizer unit and focused by the condenser lens group 6, and then, forms a uniform light field on the back focal plane of the condenser lens group 6. The uniform light field is imaged onto the mask 9 by the illumination lens group 8 after passing through the scanning slit 7, the scanning slit 7 scans the uniform light field on the back focal plane of the condenser lens group 6 so that the light field on the mask is correspondingly scanned. The scanning speed of the scanning slit 7 is very fast, up to several hundred millimeters per second, and generates certain vibration to affect the mask 9, thereby affecting the performance of lithography system, so it is necessary to introduce the illumination lens group 8 to separate the scanning slit and the mask. The illumination lens group 8 generally has large aperture (nearly 300 mm) and many lenses (10 pieces or so), which reduces the system's transmittance, reduce energy usage ratio, and makes the structure complex.